As an automobile seat, there is proposed an automobile seat which includes a height adjusting device provided between first and second pairs of spaced apart base brackets, mounted on a pair of first and second spaced apart upper rail members of a slide rail mechanism, and a pair of first and second spaced apart side frame sections of a frame for a seat cushion of the seat.
The height adjusting device includes two pairs of forward and rearward linkage arms, the forward linkage arms being bridged between the side frame sections and the first pair of spaced apart brackets, the rearward linkage arms being bridged between the side frame sections and the second pair of spaced apart brackets, a linkage rod connected, via a first support pin, at a rearward end portion thereof to one of the rearward linkage arms which is arranged on the side of the first side frame section, a first connection shaft interconnecting the forward linkage arms, a second connection shaft interconnecting the rearward linkage arms, and an actuating mechanism which includes an operation knob arranged outside the first side frame section of the seat cushion frame and having a rotating shaft rotatably penetrated through the first side frame section, a pinion gear arranged inside the first side frame section and mounted around an end portion of the rotating shaft of the operating knob which is projected inward from the first side frame section, and a sector gear arranged inside the first side frame section and meshed with the pinion gear (Japanese Patent Application Laid-Open No. 2001-138780 and WO2004/094180A1).
In the height adjusting device, the sector gear is supported at a base portion thereof to the first side frame section by a second support pin, and the linkage rod is connected at a forward end portion thereof to the sector gear by a third support pin. When the operation knob is rotated in a counterclockwise direction or a clockwise direction, the pinion gear and the sector gear are rotated to thereby draw the linkage rod in such a manner to cause the linkage rod to be moved forward or rearward according to the rotation direction of the operation knob. Synchronously with such movement of the linkage rod, the forward and rearward linkage arms are pivoted so as to rise up or pivoted so as to be collapsed according to the rotational direction of the operation knob.
In the actuating mechanism of the height adjusting device, the components of the actuating mechanism are supported or connected by many support pins and the number of the components is thus increased, so that much time is required for assembling of the actuating mechanism, thus resulting in increase of the assembling cost.
As a height adjusting device for an automobile seat, there is known a height adjusting device which is configured so as to lift the automobile seat up with resort to rotational torque exerted by a spiral spring (Japanese Patent Application Laid-Open Nos. 2000-108734 and 2000-127813).
In the actuating mechanism including the pinion gear and the sector gear which have been discussed above, a spiral spring may be also employed. From the viewpoint of operation-load, it is preferable that the spiral spring is provided so as to facilitate rotation of the sector gear. In the installation structure of the sector gear which has been discussed above, the spiral spring may be stretched between the second support pin for causing the sector gear to be supported to the first side frame section, and the third support pin for causing the linkage rod to be connected to the sector gear.
If the spiral spring is stretched between the second and third support pins as discussed above, an innermost end of the spiral spring may be retained around an end portion of the second support pin which is projected inward from the sector gear, but an outermost end portion of the spiral spring is required to be retained around an axial portion of the third support pin, interconnecting the linkage rod and the sector gear, which is located between the linkage rod and the sector gear. Such an arrangement of the spiral spring not only requires a lot of work to assemble a peripheral structure around the sections to which the spiral spring is retained, but also prevents easy replacement of the spiral spring.
The second support pin supporting the sector gear is required to have a large diameter from the viewpoint of rigidity. In addition, there is a limitation on an offset amount between the second support pin of the sector gear and the third support pin of the linkage rod, so that it is impossible to obtain an installation space for a spiral spring of a large spring constant.